1. Field of Invention
This invention relates to video transmission format conversion systems, and in particular to an automatic video detector for automatically detecting the transmission format of a broadcast video signal.
2. Related Art
At present, television systems across the world are different and the world is divided into three television transmission format standards that are basically incompatible: NTSC, PAL, and SECAM. Of these three formats, the two most popular transmission formats are NTSC (“National Television System Committee”), utilized in the United States, Canada, Mexico, parts of Central and South America, Japan, Taiwan, and Korea and the world dominant PAL (“Phase Alternating Line”) transmission format, used in most of Western Europe (except for France), China, India, most of Africa, and most of the Middle East. The third transmission format SECAM (“Sequential Couleur Avec Memoire” or in English “Sequential Color with Memory”) is a French based transmission format that is generally used in France, Russia, Eastern Europe, and some parts of the Middle East.
The NTSC transmission format is based on a 525 line, 59.94 fields/29.97 frames-per-second at 59.94 Hz system for transmission and display of video images. NTSC is an interlaced system in which each frame is scanned in two fields of 262.5 lines per field, which is then combined to display a frame of video with 525 scan lines. The PAL transmission format is based on a 625 line, 50 field/25 frames a second, 50 HZ system. The PAL signal is interlaced, like NTSC, into two fields having 312.5 lines per field each. Similarly, SECAM is a 625 line, 50 field/25 frames per second interlaced system, but the color component is implemented differently than either PAL or NTSC. Generally, SECAM uses the same bandwidth as PAL does, but transmits the color information sequentially.
Generally, NTSC, PAL, and SECAM transmission formats are incompatible because each transmission format is based on different frame rates and color transmission formats. Additionally, there are numerous variations to NTSC, PAL, and SECAM transmission formats such as, for example, NTSC-M, NTSC-J, NTSC-4.43, PAL-B, PAL-D, PAL-G, PAL-H, PAL-I, PAL-M, PAL-N, and PAL-Nc, SECAM, ME-SECAM, and D-SECAM. These various transmission formats cause incompatibility issues with many video display and recording systems because video display and recording systems (such as a televisions, video recorders, and computers with built-in television tuners) from one part of the world generally will not function properly in another part of the world. These incompatibility issues become more pronounced at border nations such as, for example, Germany, Italy, Switzerland, Belgium, Spain and France, where France utilizes SECAM and the other border nations utilize PAL.
Attempted solutions to receiving these conflicting transmission formats have included producing “multi-system capable” (i.e., systems capable of receiving multiple transmission formats) devices such as video display and recording systems with multi-system capabilities. However, at present, many multi-system capable devices do not have the capability to automatically detect the received transmission format and configure the system without external information from either a manufacturer or an end-user or in a way that quickly determines the transmission format of the received signal.
At present, multi-system capable devices are only able to determine whether an input signal is either a 525-line or a 625-line format transmission without distinguishing whether the input signal is one of approximately 11 major transmission formats such as, for example, NTSC, NTSC-J, PAL-B, PAL-D, PAL-G, PAL-H, PAL-I, PAL-M, PAL-N, and PAL-Nc, or SECAM. As a result, end-users need to specify which first transmission format to assume if the multi-system capable device detects an input signal with 525-line format, and which second transmission format to assume if the multi-system capable device detects another input signal with 625-line format. These solutions are less flexible across different regions, especially in Europe where it is important to separate between PAL and SECAM. Therefore, there is a need for a system and method capable of automatically detecting the transmission format of broadcast video signals without external information.